Patent GB-1356564-A (GB)
Title: Composite tube production
IPC: B29C53/84
Filed: 1970-09-01
Abstract: 1356564 Composite tube IMPERIAL CHEMICAL INDUSTRIES Ltd 23 Aug 1971 [1 Sept 1970] 41735/70 Heading F2P A method of preparing a composite tube comprises rotating a rigid core tube about its longitudinal axis and moving the said tube along said axis, at the same time offering a flexible ribbon, coated with a foamable composition, tangentially to the rotating tube and at an angle of less than 90 degrees to the said axis so that the edges of axially adjacent turns of the coated ribbon are generally in overlapping or butt alignment with each other and form a helically wound envelope or sheath around the tube with the foamable composition in the annulus so formed, and allowing the foamable composition to foam and cure, characterized in that at least one of the surfaces of the rigid tube and/or ribbon is provided with a coating of a substantially tack-free heat sensitizable adhesive prior to the application of the foam, and the adhesive is subsequently heated whereby the rigid tube and/or ribbon is bonded to the foam. As shown in Fig. 1 the inner tube is wound from tapes 2, 3 on to mandrel 1, and the flexible ribbon 4 having a foamable composition 6 thereon is offered thereto. A sealing strip 5 covers the seam of the wound sheath, but an internal bridging strip may be used or no bridging strip may be used. All surfaces shown hatched are coated with tack-free adhesive, but different adhesive compositions may be used on different surfaces (e.g. thermoplastics on the ribbon and isocyanate on the core tube). Hot air is passed through holes (not shown) in the mandrel and a radiant heater 7 may also be used. Materials: (a) The inner tube and flexible sheath.-Paper, cardboard, woven fibres, unwoven fibres, textile fibre, non-textile fibre, metal, plastics, glass reinforced plastics, plastics coated paper, plastics coated metal foil, corrugated cardboard or asbestos faced with metal foil or paper or faced with surfaces made of the same material as the corrugated material. The material may be treated with colouring agent, waterproofing, rat resistant agent, size. Hessian or glass fibre fabric may be treated with thermosetting resin and cured after winding into tubular form. The material may be formed with longitudinal and/or transverse ribs on one or both surfaces. (b) Sealing strip (5).-As (a) above except where rigidity or thickness are unsuitable (e.g. corrugated sheet or laminated corrugated sheet). (c) Foamable composition.-Thermoplastic polymeric material: polyamides, polyesters, polyacetal, polycarbonates, polysulphones, polymers and copolymers of ethylenically unsaturated monomers (e.g. ethylene, propylene, 4-methyl pent-1-ene, styrene, vinyl chloride, acrylonitrile, butadiene, acrylic esters). Curable polymeric materials: curable polyurethanes, phenol/formaldehyde resins, epoxy resins, systems having at least one polymerizable vinyl ether containing at least two vinyl groups per molecule, polyisocyanurates. The foams may be flexible or rigid, open cell or closed cell and may be applied hot or cold. (d) The adhesive.-Thermosetting plastics based on isocyanate and epoxy resins with or without addition of modifying agents such as polyesters. The adhesive preferably cures between 80‹ and 120‹ C. They may be applied in solvent or under solvent free conditions, and a chemical activator may be used if desired. Thermoplastic adhesives having tacky properties between 50‹ and 150‹ C. and preferably between 80‹ and 120‹ C. may be used by polyvinyl acetate, polyvinyl chloride, polyolefins (polyethylene) and their copolymers. When polyurethane foams are used it is preferred that non-aqueous adhesives are used and it is also preferable to prevent ingress of moisture, e.g. by using a water impervious adhesive or by using materials having a waterproof coating (e.g. polythene) for forming the inner tube and outer sheath.